The present invention relates to a control system arranged to overlap a high-frequency signal on a power line when performing communications on a power line.
The conventional air conditioning system is composed to have one or more outdoor units, one or more indoor units, a three-phase and a single-phase power lines for supplying electric power to these units, a refrigerant piping for exchanging refrigerant between the indoor units and the outdoor units, a bus wiring transmission line for exchanging control information between the indoor units and the outdoor units, and a remote controller for operating the indoor units. The control information of the air conditioning system includes an indication of on or off of a power supply or “in operation” of the indoor unit, a set room temperature and a current temperature, operating conditions of the outdoor unit and the indoor unit, and so forth. These pieces of data also include a header composed of address information of a transmission source and a receiving destination, a type, a size and a number of a message as well as a trailer such as error-correcting information, all of which are added to the data. The resulting data is communicated in the form of packets. In the conventional air conditioning system, a leased communication line has been provided as its communicating method. Today, it is known that a technology of using the power line for the leased communication line has been developed for saving resources and installing work.
As an electric power communication system of transmitting the high-frequency signal via the power line, the following lighting system has been proposed. A plurality of branch power lines are secured as communication regions by separating them with a blocking filter. A gate way is located to and connected with each of these communication areas and a high-speed communication line is connected between the gate ways so that the control information may be exchanged between the outside and the inside of the communication region. See the Japanese Official Gazette of JP-A-02-281821 which shows the load controlling (PLC) in the lighting system. This document does not concern the air conditioning system wherein communications are concentrated. As a power line of the lighting system, a high-speed leased communication line is used because the communication capacity required for communicating data between the gateways in the communication based on the power line (referred to as the power line communication) is not enough. In the air conditioning system, however, the communication capacity of the system is determined not from the communications traffic between the similar communication regions but from the communications traffic between the indoor unit and the outdoor unit. Hence, the power line of the lighting system does not hold true to the air conditioning system as it is. Further, the power line communication to a large-scaled air conditioning system and the communications between different phases are disclosed as well. This technology is arranged to connect a power line communication area of an outdoor unit having a three-phase power line as a communication path and a power line communication area of an indoor unit having a single-phase power line as a communication path through a bridge in a wireless or a wired manner with the leased communication path. (See the Official Gazette of JP-A-2002-243248.)